Dynamic RxDiv for Idle Mode in a User Equipment

ABSTRACT

A method of evaluating a reception quality of a receiver includes determining a reception quality of the receiver using a measurement from a single active antenna of the receiver if the receiver is in the idle mode. The method further includes activating receiver diversity by activating at least a second antenna of the receiver in the idle mode if the measurement from the single active antenna of the receiver is below a first predetermined reception quality threshold. A receiver includes receiver chains configured to interface with respective antennas, and a reception quality estimation unit configured to determine a reception quality of a single active receive chain when the receive is in an idle mode. The receiver further includes a diversity controller configured to selectively activate at least a second receive chain in the idle mode based on the determined reception quality from the reception quality estimation unit.

FIELD

This invention relates to a user equipment (UE) performing a dynamicactivation/deactivation of receive diversity (RxDiv) in an idle mode,and a method of dynamically activating and deactivating receivediversity in an idle mode.

BACKGROUND

In mobile communications between a base station (BS) and a userequipment (UE), diversity receivers are used in the user equipment toimprove the reception of radio signals sent by the base station.Therefore diversity receivers improve the quality of the receivedsignal. The use of receive diversity, however, leads to significantlyincreased power consumption, considerably reducing the availablestand-by.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 is a block diagram illustrating a user equipment employingreceive diversity according to one embodiment.

FIG. 2 is a block diagram illustrating a portion of the receiver of FIG.1.

FIG. 3 is a block diagram illustrating a portion of the receiver of FIG.1.

FIG. 4 is a graph illustrating an example of selectively activatingreceive diversity in an idle mode in a user equipment according to oneembodiment.

FIG. 5 is a graph illustrating an example of selectively deactivatingreceive diversity in an idle mode in a user equipment according to oneembodiment.

FIG. 6 is a flow chart illustrating a method of dynamically activatingreceive diversity in the idle mode based on identification ofpredetermined criteria in a user equipment according to one embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

As employed in this Specification, the terms “coupled” and/or“electrically coupled” are not meant to mean that the elements must bedirectly coupled together; intervening elements may be provided betweenthe “coupled” or “electrically coupled” elements.

User equipments are devices that may include antennas, receivercircuits, and transmitter circuits, and may includesignal-to-interference-ratio (SIR) estimation units, diversitycontrollers and memory are described below.

Antennas are transducers that transmit or receive electromagnetic waves.In other words, antennas convert electromagnetic radiation intoelectrical current, or vice versa. Antennas generally deal in thetransmission and reception of radio waves. Antennas are used in systemssuch as radio communications, wireless LAN, cell phones and mobilecommunications. Antennas in the user equipment receive radio signalsfrom a base station and convert these signals into electrical signalsthat are the received signals.

Radio signals are radio frequency signals that are radiated by a radiotransmitter (sender) with a radio frequency (RF) in the range of about 3Hz to 300 GHz, for example. This range corresponds to the frequency ofalternating current electrical signals used to produce and detect radiowaves.

The use of multiple antennas in a user equipment results in improvedoverall system performance due to the use of diversity techniques.Receiver diversity (RxDiv) or antenna diversity, is a wireless diversityscheme that uses two or more antennas to improve the quality andreliability of a wireless link. In some instances, such as in urban andindoor environments, there is not a clear line-of sight (LOS) betweenthe transmitter and the receiver. Instead, the signal is reflected alongmultiple paths before finally being received. Each of these bounces canintroduce phase shifts, time delays, attenuations, and even distortionsthat can destructively interfere with one another at the aperture of thereceiving antenna. Receive diversity is effective at mitigating thesemultipath situations because multiple antennas offer a receiver severalobservations of the same signal. Each antenna will experience adifferent interference environment. Thus, if one antenna is experiencinga deep fade, it is likely that another has a sufficient signal.Collectively such a system can provide a robust link.

Receiver circuits, sometimes referred to as receiver chains, are coupledto a respective antenna in order to process the received signal of theantenna. Receiver circuits may include Rake receivers and/or equalizersor other suitable receivers.

Downlink signals are signals transmitted in downlink direction, i.e.from a base station to the user equipment. Downlink signals carrydownlink channels. In WCDMA a user terminal may be allocated one or moreData Channels (DCHs) or Dedicated Physical Data Channels (DPDCHs) whichcarry user bits. A user terminal may also be allocated a PhysicalControl Channel (PCCH) or a Dedicated Physical Control Channel (DPCCH)on which overhead control information is carried to the user, e.g. bitrate information of the associated DCHs, transmit power control bits andpilot symbols, which can be used to perform the noise measurements, suchas SIR measurements, in the fast power control loop process.

Rakes are rake receivers or generalized-rake (G-Rake) receivers thatexploit multi-path information of the received radio signal. A rake canbe utilized to counter the effects of multipath fading. This can beachieved by using several sub-equalizers or “fingers”, that is, severalcorrelators each assigned to a different multi-path component. Eachfinger independently equalizes a single multi-path component, and at alater stage the contribution of some or all fingers are combined inorder to make use of the different transmission characteristics of eachtransmission path. This results in a higher signal-to-noise ratio in amulti-path environment. By using rakes, different paths with differentdelays can be effectively combined to obtain the path diversity gain.Due to narrow transmission pulses and a large transmission bandwidth ofthe radio channel, the resulting inter-symbol interference (ISI) and along delay spread in the characterization of the radio channel may beovercome by using the rake. A rake output signal is provided at anoutput of the rake.

Equalizers equalize effects of the radio channel on the received radiosignal, such as delay or multipath fading by applying the inversechannel impulse response to the received signal in order to reconstructthe original transmitted signal. The inverse of the channel impulseresponse may be stored in an array, e.g. forming an FIR filter and maybe updated by an adaptive algorithm. An estimation of the transmittedsignal is provided as equalized signal at an output of the equalizer.

Receiver circuits (i.e., receiver chains) may include mixers for mixingthe received signals down to baseband, demodulators for demodulating thereceived signals and decoders for decoding the received signals.Demodulation is the inverse operation of modulation which is performedin the base station transmitter, e.g. a UMTS transmitter. By way ofexample, the modulation scheme (constellation) in UMTS transmitters isquadrature phase shift keying (QPSK) or quadrature amplitude modulation,e.g. 16QAM or 256QAM. Modulation is a process where the transmittedsymbols are multiplied with the carrier signal obtaining a signal to betransmitted. Demodulation is the inverse process multiplying thereceived signal with the carrier signal to obtain the originaltransmitted symbols. The modulating symbols are called chips, and theirmodulating rate may, for example, be 3.84 Mcps.

Quality estimation units perform estimates of various performancecriteria associated with the user equipment to ascertain a noiseenvironment as well as other conditions associated therewith. Thequality measure may be a signal-to-noise ratio (SNR), asignal-to-interference-plus-noise ratio (SIR), an absolute power of thedownlink signal measured at the user equipment, an error rate or anyother quality measure. The quality estimator may monitor known signalpatterns such as pilot symbols in the received downlink signal over aspecified time interval in order to estimate a quality measure. Asstated above, one type of quality estimation unit is asignal-to-interference-plus-noise-ratio (SIR) estimation unit (sometimesalso called an SINR). SIR estimation units perform estimation of SIRvalues of the downlink signals after demodulation. Thesignal-to-interference-plus-noise ratio (SIR) is the quotient betweenthe average received modulated signal power and the sum of the averagereceived interference power and the received noise. The interferencepower may be generated by other transmitters than the useful signal.Interference is anything which alters, modifies, or disrupts a signal asit travels along a channel between a source and a receiver. In WidebandCDMA systems, this kind of interference is frequently called other-cellinterference. Additionally, there is own-cell interference or inter-pathinterference. In a frequency selective transmission channel, the signaltravels from the transmitter to the receiver along differenttransmission paths which are characterized by different propagationdelays and uncorrelated fading. These multiple transmission pathsinterfere with each other, hence the resulting interference is calledinter-path interference. Another type of quality estimation unit simplymeasures received signal power. Other types of estimating receptionquality also exist, and such variations are all contemplated as fallingwith the scope of the present disclosure.

SIR estimation is performed by an SIR estimation unit which may be anelectrical circuit for estimation of SIR. The SIR estimation unitestimates the received power of the downlink channel to be powercontrolled and the received interference and noise on this downlinkchannel. For DPCH channels, the signal power and the interference andnoise power may be estimated by using pilot symbols, i.e., known symbolstransmitted on one or more downlink channels.

Diversity controllers are used to control diversity receivers includingreceiver circuits. Diversity receivers enhance reliability by minimizingthe channel fluctuations due to fading. The central idea in diversity,as highlighted supra, is that different antennas receive differentversions of the same signal. The chances of all these copies being in adeep fade is small. This solution therefore is advantageous when thefading is independent from element to element, and are of limited use(beyond increasing the SNR) if perfectly correlated (such as inline-of-sight conditions). Independent fading would arise, for example,in a dense urban environment where the several multipath components addup very differently at each element.

Each receiver element or receiver chain of a diversity receiver,therefore, receives an independent sample of the random fading process,i.e., an independent copy of the transmitted signal. In the diversityreceiver these independent samples are combined under control of thediversity controller in order to achieve the desired goal of increasingthe SNR and reducing the bit error rate (BER). The diversity controllermay select individual receiver circuits in the diversity receiver fordata processing. The diversity controller may control the way ofcombining these samples, for example selecting “Maximum Ratio Combining”(MRC), i.e. obtaining weights that maximize the output SNR, selecting“Selection Combining” (SC), i.e. choosing the element with the greatestSNR for further processing or selecting “Equal Gain Combining” (EGC),i.e. setting unit gain at each element. The diversity controller mayfurther control the power of the diversity receiver by turning offreceiver circuits which provide poor SNRs or BERs in order to save powerand by turning on receiver circuits which provide good SNRs or BERs inorder to improve the detection quality of the diversity receiver. Thediversity controller may control the power switching of the receivercircuits depending on a quality measure of the quality estimator.

Operation of a user equipment (UE) may be summarized generally asfalling under two modes (1) a data channel mode in which a dedicated DCHconnection is established, and (2) an idle mode in which no dedicatedDCH connection exists. During the idle mode, the UE periodicallymeasures the reception quality, and if the reception quality drops belowa certain threshold, as specified by the network, some correctiveaction, such as a handover to another network, is initiated. A handoverto another network is not necessarily an issue for the customer forvoice calls because often such a change (e.g., handover from a 3Gnetwork to a 2G network) is transparent to the customer. However, such ahandover can be disadvantageous for a data call that requiressignificantly higher data throughput. In addition, for a networkoperator, switching to another network that is not your own may incursignificant roaming charges and is thus undesirable.

In the Idle mode reception quality measurements are made, however suchmeasurements are not made using receive diversity. Using receivediversity in the idle mode can improve the reception qualitymeasurement. Consequently, this improvement effectively increases thecoverage of a given network by reducing a frequency of a networkhandover. The improvement in reception quality also improves thereception of pagings and thus results in a reduction in missed calls.

Enabling receive diversity throughout the entire idle mode would enablethe above-described improvements, however, receive diversitysignificantly increases power consumption (e.g., up to about a 30%increase), and thus drastically reduces the standby time of the UE. Thepresent disclosure is directed to a system and method of dynamicallyenabling and disabling receive diversity (RxDiv) when necessary in theidle mode to achieve the benefits highlighted above while minimizing thedeleterious increase in power consumption. The present disclosureselectively enables and disables RxDiv based on the availability ofreception quality measurements associated with an active antenna and onRxDiv measurements, as will be more fully appreciated in the discussionaccompanying the figures below.

FIG. 1 schematically illustrates a portion of user equipment (UE) 100according to one embodiment, in particular a user equipment 100 which isconfigured to dynamically enable and disable receive diversity (RxDiv)in the idle mode. The UE 100, which may also be referred to as areceiver, includes a plurality of receiver chains 102 a, 102 b thatreceive an incoming signal (i.e., a downlink signal) at a respectiveantenna 104 a, 104 b. In one embodiment, the receiver 100 has tworeceiver chains, 102 a, 102 b, however, “n” receiver chains, wherein “n”is an integer greater than one, may be employed in the receiver and iscontemplated by the present disclosure. The receiver chains 102 a, 102b, perform various receive functions as highlighted above, such asdemodulating the received signal, etc. The received signal of eachreceiver chain 102 a, 102 b is evaluated by a respective qualityestimation unit 106 a, 106 b. As discussed generally above, the qualityestimation units 106 a, 106 b measure a characteristic of the receivedsignal and communicate that characteristic to a diversity controller 108as a reception quality value 110 a, 110 b.

Still referring to FIG. 1, in the idle mode (i.e., when no dedicated DCHconnection is established) the diversity controller 108 receives areception quality value 110 a or 110 b from one of the qualityestimators 106 a or 106 b, respectively, depending on which of the twoantennas 104 a and 104 b is active. The diversity controller 108compares the reception quality value to a predetermined threshold value.If the reception quality falls below the predetermined threshold valuein the idle mode, the diversity controller 108 activates the RxDiv modeby control signals 114 a or 114 b to activate or enable the other of thereceiver chains that was previously inactive. For example, if the firstreceiver chain 102 a was originally active and the receiver chain 102 bwas inactive, upon the reception quality value received at 106 a fallingbelow the predetermined threshold value, the diversity controller 108enables the second receiver chain 102 b via control signal 114 b suchthat two receiver chains are active, thus establishing a receivediversity (RxDiv) condition.

In one example, only two receiver chains exist. More generally, aplurality of receiver chains may exist, wherein “n” is greater than one.In the event that three or more receiver chains exist, if the activereceiver chain receives a reception quality value that is less than thepredetermined threshold value, the diversity controller may activatejust one additional receiver chain rather than all of them to seewhether a reception quality with just a single additional activatedreceiver chain is sufficient to provide a reception quality that exceedsthe threshold. The diversity controller may limit itself to activatingjust one additional receiver chain in one embodiment, or mayincrementally activate one additional receiver chain at a time until theRxDiv reception quality increases above the threshold in anotherembodiment. In yet another alternative embodiment, the diversitycontroller may automatically activate all available receiver chains uponone of them having a reception quality below the threshold in the idlemode. All such variations are contemplated as falling within the scopeof the present disclosure.

In one embodiment, the diversity controller 108 employs a fixedpredetermined threshold, while in another embodiment, the diversitycontroller 108 employs a predetermined threshold from a memory unit 112that contains a plurality of different values in a table, for example.In one embodiment, the diversity controller 108 selects a particularthreshold value from the memory 112 based on the network presentlyutilized by the UE. For example, if a given network specifies that if areception quality falls below −80 dBm, a handover to another networkmust take place, the diversity controller may select a predeterminedthreshold of −80 dBm, or based on a user-specified safety guardband, thediversity controller 108 may select a threshold value of −78 dBm fromthe memory 112. In another embodiment, if the receiver 100 is operatingin another network that employs a different threshold value, thediversity controller 108 may select a different threshold value from thememory 112.

As can be seen from FIG. 1, the receiver 100 selectively activates thereceive diversity mode based on the reception quality via the diversitycontroller 108. Further, because the diversity controller 108 relies onthe reception quality measurement(s) from the quality estimation units106 a, 106 b, receive diversity is only employed in the idle mode whenneeded, and thus the amount of power consumption is minimized. Inaddition, after the receiver 100 enters the diversity mode, thereception quality of RxDiv is evaluated, and if the reception quality ofthe receiver in RxDiv falls below the predetermined threshold level, thecorrective action dictated by the network in which the UE resides willthen take place. For example, in the event the RxDiv reception qualityfalls below the threshold, a network handover of the UE will then takeplace (e.g., a handover from the 3G network to a 2G network).

In addition to the above, once the receiver 100 enters RxDiv, thequality estimation units 106 a, 106 b continue to report the receptionquality in RxDiv as well as the reception quality of the individualreceiver chains associated with the active antennas. If the receptionquality of one of the active antennas is sufficiently good (i.e.,greater than the predetermined threshold), the diversity controller 108will keep the receiver chain associated with the one antenna active,while deactivating the other presently active receiver chains. In thismanner, the diversity controller 108 actively evaluates the receptionquality of the system, and dynamically activates and deactivatesreceiver chains in the idle mode to improve reception quality only whenneeded. In one example, if during RxDiv the reception quality is abovethe threshold, and the reception quality of the receiver chain 102 bassociated with antenna 104 b is also above the threshold, but thereception quality of the receiver chain 102 a associated with theantenna 104 a is below the threshold, the diversity controller 108 willdeactivate the receiver chain 102 a while keeping the receiver chain 102b active, thereby exiting the RxDiv state in the idle mode. In the abovemanner, the diversity controller can move dynamically enable and disableRxDiv to improve reception quality when needed, yet do so whileminimizing power consumption in the idle mode.

Referring now to FIG. 2, a portion of the receiver 100 shown in FIG. 1is illustrated in somewhat greater detail. For example, in the receiverchain 102 a a demodulator 202 a is illustrated. The receiver chain 102 amay include other components as well. The received demodulated signal isnoted at reference number 204 a, and is provided to the qualityestimation unit 106 that, in one embodiment, includes a plurality ofmeasurements units 206 a, 206 b and 206 c. Likewise, the second receiverchain 102 b includes a second demodulator 204 b, which is fed to thequality estimation unit 106.

In one embodiment, the receiver 100 includes only measurement units 206a and 206 b that operate to measure a reception quality of just onereceiver chain associated therewith. In such instances, during the RxDivcondition the diversity controller 108 employs the individual antennareception quality measurements to generate a RxDiv reception quality.More detail regarding this feature will be provided infra. In anotherembodiment, the quality estimation unit 106 includes a third measurementunit 206 c that receives the reception quality data from the othermeasurement units 206 a and 206 b. In this manner a more sophisticatedRxDiv reception quality determination can be made.

In the example illustrated in FIG. 2, the reception quality is evaluatedusing a signal-to-interference-plus-noise ratio (SINR) calculation.Alternatively, a signal-to-noise ratio (SNR) or a signal power (S)measurement may be made, or any other suitable measurement thatcharacterizes the reception quality may be employed and all suchalternatives are contemplated as falling within the scope of the presentdisclosure.

FIG. 3 illustrates another portion of the receiver 100 of FIG. 1 ingreater detail. In FIG. 3 the diversity controller 108 receives from thereception quality measurement unit 106 either a single reception qualityparameter 110 c or a plurality of quality reception parameters 110 a and110 b that comprise values associated with individual antennas 104 a,104 b. In one embodiment of the disclosure, quality parameter 110C maycomprise a combined quality parameter (e.g., a SNR) when the receiver isin receive diversity. In one example, this may simply a sum of each ofthe active receiver chains. The diversity controller 108 utilizes thedata it receives from the reception quality measurement unit 106 todynamically enable or disable RxDiv in the idle mode.

In the instance when the UE 100 enters the idle mode, no RxDiv exists,and thus either antenna 104 a or antenna 104 b is active. Thus thediversity controller 108 operates to deactivate one of the receiverchains 102 a, 102 b. In one example, antenna 104 a and receiver chain102 a are active, and antenna 104 b and receiver chain 102 b areinactive. Thus during the idle mode the reception quality measurementunit 106 evaluates the reception quality thereof, and communicates thereception quality at 110 a to the diversity controller 108.

The diversity controller 108 compares the reception quality value 110 a,or a value associated therewith, to a predetermined threshold 400, asillustrated in FIG. 4. In the embodiment of FIG. 4, the predeterminedthreshold 400 is a value received from the threshold table 302 from thememory 112 illustrated in FIG. 3. In this embodiment, the threshold 400is the same threshold dictated by the network to force a networkhandover, however, this threshold may differ, as will be seen in afurther embodiment later. As can be seen in FIG. 4, at a time periodbefore 402, the reception quality value 110 a is greater than thethreshold 400, and thus the diversity controller 108 makes no changes.At measurement time instant 404 the reception quality value 110 a dropsbelow the predetermined threshold 400, and the diversity controller 108initiates an activation of receive diversity RxDiv by generating andtransmitting a control signal 114 b that activates the second receiverchain 102 b. Consequently, at the next measurement instant an RxDivquality reception value 406 is calculated by the diversity controller108 based on the reception quality values from antennas 104 a and 104 b.As can be seen at 408, while the quality reception values of bothantenna 104 a and antenna 104 b are each below the threshold value 400,the RxDiv value 406 is above the threshold 400, and thus a handover toanother network is avoided that would otherwise have occurred. Theimprovement in reception quality between the single antenna 104 a andthat achieved by the reception diversity is referred to as the RxDivgain, and is shown at reference numeral 410 in FIG. 4.

As illustrated in FIG. 4, the RxDiv value 406 maintains a value greaterto or equal than the predetermined threshold 400 until measurement timeinstant 412, when the value 406 drops below the threshold 400. At suchtime, the diversity controller 108 initiates a network handover as thecorrective action to remedy the problem of unacceptable receptionquality. If, however, the RxDiv value 406 had stayed above the threshold400, a network handover would have advantageously been avoided.

According to one embodiment of the disclosure, the diversity controller108 comprises a processing unit 304, wherein an RxDiv value 406 iscalculated using the individual reception quality values 110 a and 110 bfrom the active receiver chains 102 and 102 b in receiver diversitymode. In one embodiment the processing unit 304 calculates RxDiv value406 as:

MeasRxDiv=MeasAnt104a+MeasAnt104b=110a+110b.

Alternatively, RxDiv value 406 is calculated as follows:

MeasRxDiv=max(MeasAnt104a,MeasAnt104b)+3 dB, or

MeasRxDiv=mean(MeasAnt104a,MeasAnt104b)+3 dB, or

MeasRxDiv=min(MeasAnt104a,MeasAnt104b)+3 dB.

The diversity controller 108 employs the processing unit 304 tocalculate the RxDiv value 406 (MeasRxDiv) and then initiate a correctiveaction only if that value falls below the predetermined threshold.

Still referring to FIG. 4, note that at a time instant after 404, thereception quality calculated by the diversity controller isdiscontinuous, wherein at time instant 404, the value of antenna 104 adropped below the threshold 400, and at the next time instant, uponactivation of receive diversity, the value of RxDiv is substantiallyabove the threshold 400. To avoid triggering a handover at 404 due tothe reception quality falling below the threshold 400, in one embodimentthe diversity controller 108 reports to the network a value equivalentto the threshold 400, i.e., a “fake” reporting at 404 to avoidtriggering a handover and allowing time to initiate receiver diversity.This is reflected in the bold line in FIG. 4 as indicative of the valuereported by the diversity controller 108 to the network and to otherinternal circuitry of the receiver 100 while the actual value maydiffer. In addition, to avoid the large, substantially discontinuousjumps in reporting reception quality to other internal receivercircuitry, in one embodiment, after the activation of RxDiv hasdramatically increased reception quality, the diversity controller 108reports a reception quality equivalent to the threshold value 400 asopposed to the RxDiv value that is substantially greater than thethreshold to avoid the discontinuity in reporting.

In an alternative embodiment of the disclosure illustrated in FIG. 5, apredetermined threshold 500 is selected that is greater than thethreshold 400 dictated by the network. In this embodiment, the receiver100 has one antenna 104 a active and a reception quality value 110 a iscommunicated to the diversity controller 108. At measurement timeinstant 504, the reception value 110 a falls below the predeterminedthreshold 500 specified by the UE, but is not below the network mandatedthreshold 400. In this context, the network threshold 400 may beconsidered a first predetermined threshold and the internal receiverthreshold 500 is a second predetermined threshold that is greater thanthe first predetermined threshold. Once the reception quality 110 a ofthe single antenna 104 a drops below the second threshold 500, thediversity controller 108 activates or enables receive diversity byactivating the second receiver chain 102 b via a control signal 114 b.At the next measurement time instant after 504 RxDiv has been activatedand the diversity controller 108 receives reception quality values 110 aand 110 b from both active antennas 104 a and 104 b. From these values aMeasRxDiv is calculated and is shown in FIG. 5 at reference numeral 406.Since the diversity controller 108 enables receive diversity uponcrossing the second threshold 500, the improvement in reception qualityoccurs before the first threshold 400 is crossed, and no “fake”reporting occurs at 504, in contrast to the embodiment of FIG. 4. Thediversity controller 108 in FIG. 5, however, does continue to report areception quality at the second predetermined threshold 500 to internalreceiver circuitry to avoid the substantial discontinuity jump inreception quality that in actuality occurred after time instant 504 dueto the RxDiv.

Due to the receive diversity RxDiv value 406, the receiver 100 avoids anunnecessary network handover. Over time, if the reception quality inRxDiv falls below the first predetermined threshold 400 (i.e., thenetwork mandated threshold), for example, as shown at reference numeral512, the diversity controller 108 reports the value and initiates anetwork handover.

Once a network handover has occurred, it is still desirable to returnback to the original network if possible, for example, to discontinueincurring roaming charges or to utilize the higher throughput of theoriginal network. In any event, the diversity controller 108periodically activates RxDiv and makes a measurement 406. If theMeasRxDiv values are below the threshold 400, no action is taken,however, if the value 406 reaches the threshold 400 (e.g., as shown atmeasurement time instant 602), the diversity controller 108 initiates anetwork handover back to the original network. In addition, while RxDivis active, the diversity controller 108 continues to evaluate thereception quality values 110 a and 110 b of the individual antennas 104a and 104 b. If either one of the antennas exhibit a reception quality110 a and 110 b that meets the threshold 400, the diversity controller108 deactivates receive diversity by deactivating the receiver chainthat does not exhibit a reception quality above the threshold. In theexample illustrated in FIG. 6, at measurement time instant 604 the firstantenna 104 a and first receiver chains 102 a exhibits a receptionquality value 110 a that meets the threshold 400. At that time thediversity controller 108 deactivates the receiver chain 102 b to disablereceiver diversity and thus the actual reception quality 110 a of thefirst antenna 104 a is reported at the next measurement instant 606.Note that in the embodiment of FIG. 6 the threshold at which RxDiv isdeactivated is the network threshold 400, however, the threshold mayalternatively be set slightly higher than the threshold 400 to providesome hysteresis and avoid some unique situations when RxDiv getsrepeatedly activated and deactivated (i.e., when the reception qualityvalue 110 a bounces up and down about the threshold 400).

Referencing FIG. 7, a situation exists, wherein the diversity controller108 has dynamically enabled RxDiv at a time measurement instant 702 whenthe reception quality value 110 a of the receiver chain 102 a fallsbelow the predetermined threshold 400. At the next measurement instantthe RxDiv gain 410 results in a MeasRxDiv value 406 that substantiallyexceeds the threshold and a network handover is avoided. Unlike theexample in FIG. 4, at time measurement instant 704, the receptionquality 110 a of the first antenna 104 a stops declining and levels out,and at time measurement instant 706, the reception quality value 110 abegins increasing. During this time period RxDiv 406 still exceeds thepredetermined threshold 400 and so a network handover is avoided. Attime instant 708, the reception quality value 110 a of the antenna 104 areaches the threshold 400, and the diversity controller 108 disablesreceiver diversity by deactivating the second receiver chain 102 bassociated with the second antenna 104 b. Thus the embodiment of FIG. 7illustrates that throughout the idle mode, the diversity controller 108continues to dynamically activate and deactivate RxDiv to avoidunnecessary network handovers while concurrently attempting to minimizepower consumption.

According to another embodiment of the disclosure, a method 800 ofoperating a receiver in an idle mode is provided in conjunction with theflow chart of FIG. 8. While the exemplary method 800 is illustrated anddescribed below as a series of acts or events, it will be appreciatedthat the present disclosure is not limited by the illustrated orderingof such acts or events. For example, some acts may occur in differentorders and/or concurrently with other acts or events apart from thoseillustrated and/or described herein, in accordance with the invention.In addition, not all illustrated steps may be required to implement amethodology in accordance with the present disclosure.

The method 800 starts at 802, wherein a query is made whether the UE isin the idle mode. In one embodiment of the disclosure, the idle modeexists any time a dedicated DCH channel is not established with the UE.If the UE is not in an idle mode (NO at 802), the method 800 returns tothe beginning and the query is repeated. If the UE is in the idle mode(YES at 802), a reception quality is measured at 804. When the UE is inthe idle mode, receive diversity is not enabled, so the UE will receivea reception quality value associated with an active receiver chain. Inone embodiment, a system such as that illustrated in FIG. 1 may beemployed, wherein a reception quality value 110 a is received if a firstreceiver chain 102 a is active while other receiver chains (e.g., 102 b)are inactive. If the determination is negative (NO at 806), the method800 returns to 802.

At 806 a determination is made, based on the received reception qualityvalue at 804, whether receive diversity is needed. If the determinationis affirmative (YES at 806), the method 800 continues at 808, whereinreceive diversity is enabled.

In one embodiment, a diversity controller such as controller 108 in FIG.1, compares the received reception quality value (e.g., 110 a) to apredetermined threshold (e.g., from a memory 112), and enables RxDiv ifthe reception quality falls below the threshold. In one embodiment, thisthreshold is a value dictated by the network; alternatively thethreshold may be guardbanded and be a value slightly greater than thatdictated by the network.

The method 800 continues at 810, wherein the reception quality inreceive diversity (MeasRxDiv) is measured. As highlighted above, thereception quality can be measured in one embodiment as MeasRxDiv in anynumber of different ways using reception quality values of individualactive antennas, or a more sophisticated method may be employed. Thismeasured reception quality in RxDiv is then compared to thepredetermined threshold at 812. In one embodiment the reception qualityvalue can be an SNR, a signal power S, or other parameter that reflectsreception quality. If MeasRxDiv falls below the threshold (YES at 812),corrective action is taken by the UE at 814. In one embodiment, the UEinitiates a network handover. If the measured receive diversityreception quality value MeasRxDiv is not below the threshold (NO at812), the diversity controller maintains the UE in receive diversitymode, but also continues to evaluate the reception quality of eachactive receiver chain. If the reception quality of either receiver chainrises above the threshold (YES at 816), the receive diversity isdisabled at 818, and the method returns to 804. If, however, no activereceiver chain exhibits a reception quality above the threshold (NO at816), the method 800 returns to 810, wherein MeasRxDiv continues to bemonitored. In the above embodiment, the threshold employed at 816 is thesame network threshold, however, in an alternative embodiment, adifferent (e.g., higher) threshold may be employed as hysteresis.

While a particular feature or aspect of an embodiment of the inventionmay have been disclosed with respect to only one of severalimplementations, such feature or aspect may be combined with one or moreother features or aspects of the other implementations as may be desiredand advantageous for any given or particular application. Furthermore,to the extent that the terms “include”, “have”, “with”, or othervariants thereof are used in either the detailed description or theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprise”. Furthermore, it should be understood thatembodiments of the invention may be implemented in discrete circuits,partially integrated circuits or fully integrated circuits orprogramming means. Also, the terms “exemplary”, “for example” and “e.g.”are merely meant as an example, rather than the best or optimal. It isalso to be appreciated that features and/or elements depicted herein areillustrated with particular dimensions relative to one another forpurposes of simplicity and ease of understanding, and that actualdimensions may differ substantially from that illustrated herein.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. For instance,implementations described in the context of a user equipment could beapplied to WCDMA transceivers, UMTS transceivers or to mobilecommunication transceivers relating to other technical standards such ase.g. GSM, LTE or derivatives thereof or applying other multiple accessschemes such as e.g. TDMA, FDMA etc. This application is intended tocover any adaptations or variations of the specific embodimentsdiscussed herein. Therefore, it is intended that this invention belimited only by the claims and the equivalents thereof.

What is claimed is:
 1. A method of evaluating a reception quality of areceiver, comprising: determining whether the receiver is in an idlemode; if the receiver is in the idle mode, determining a receptionquality of the receiver using a measurement from a single active antennaof the receiver; and activating receiver diversity by activating atleast a second antenna of the receiver in the idle mode if themeasurement from the single active antenna of the receiver is below afirst predetermined reception quality threshold.
 2. The method of claim1, further comprising: determining the reception quality of the receiverusing a measurement from all active antennas of the receiver during theidle mode upon receiver diversity being activated; and initiatingcorrective action by the receiver if the evaluated reception qualitywith activated receiver diversity is below a second predeterminedreception quality threshold.
 3. The method of claim 2, wherein the firstpredetermined reception quality threshold and the second predeterminedreception quality threshold are the same.
 4. The method of claim 2,wherein the corrective action by the receiver comprises a handover froma present network to a different network.
 5. The method of claim 2,further comprising deactivating receiver diversity by deactivating oneof the single active antenna and the second antenna in the idle mode ifthe measurement of the reception quality associated with one of thesingle active antenna or the second antenna is greater than a thirdpredetermined threshold.
 6. The method of claim 5, wherein the thirdpredetermined reception quality threshold is greater than the firstpredetermined reception quality threshold.
 7. The method of claim 2,wherein determining the reception quality of the receiver from all theactive antennas of the receiver upon receiver diversity being activatedcomprises: measuring a first reception quality parameter associated witha first antenna of the active antennas; measuring a second receptionquality parameter associated with a second antenna of the activeantennas; and using the first reception quality parameter and the secondreception quality parameter to generate a receiver diversity (RxDiv)measurement, wherein the RxDiv measurement comprises the determinedreception quality with receiver diversity activated.
 8. The method ofclaim 7, wherein the RxDiv measurement comprises one of: an addition ofthe first reception quality parameter and the second reception qualityparameter; a larger of the first reception quality parameter and thesecond reception quality parameter; a smaller of the first receptionquality parameter and the second reception quality parameter; and a meanof the first reception quality parameter and the second receptionquality parameter.
 9. The method of claim 7, wherein the RxDivmeasurement comprises a quality parameter associated with both the firstantenna and the second antenna.
 10. The method of claim 1, whereindetermining whether the receiver is in the idle mode comprisesdetermining that no DCH connection is established in the receiver. 11.The method of claim 1, wherein determining the reception quality of thereceiver using a measurement from the single active antenna comprisesdetermining a signal power or a signal-to-noise ratio (SNR) of areceived signal from the single active antenna.
 12. A receiver,comprising: a plurality of receiver chains configured to interface witha plurality of antennas, respectively, and receive a plurality ofsignals therefrom, respectively; a reception quality estimation unitconfigured to determine a reception quality of a single active receiverchain of the plurality of receive chains when the receiver is in an idlemode; and a diversity controller configured to selectively activate atleast a second receiver chain of the plurality of receiver chains in theidle mode based on the determined reception quality from the receptionquality estimation unit.
 13. The receiver of claim 12, wherein thereception quality estimation unit is configured to determine thereception quality by measuring a signal power or a signal-to-noise ratio(SNR) of a signal from the single active receive chain.
 14. The receiverof claim 12, wherein the diversity controller is configured to activatethe at least a second receiver chain if the determined reception qualityis below a first predetermined reception quality threshold.
 15. Thereceiver of claim 12, wherein the reception quality estimation unit isconfigured to determine a reception quality associated with all activereceiver chains when the diversity controller has activated the at leasta second receiver chain, and wherein the diversity controller is furtherconfigured to initiate a corrective action if after activating the atleast a second receiver chain the determined reception quality is belowa second predetermined reception quality threshold.
 16. The receiver ofclaim 15, wherein the first predetermined reception quality thresholdand the second predetermined reception quality threshold are the same.17. The receiver of claim 12, wherein the diversity controller isconfigured to deactivate receiver diversity by deactivating one of thefirst receiver chain and the second receiver chain if the receptionquality of a remaining activated receiver chain of the first receiverchain and the second receiver chain is greater than a thirdpredetermined threshold.
 18. The receiver of claim 17, wherein if boththe first receiver chain and the second receiver chain have a receptionquality greater than the third predetermined threshold the diversitycontroller is configured to deactivate the receiver chain having alesser reception quality than the other.
 19. A receiver, comprising: aplurality of receiver chains configured to interface with a plurality ofantennas, respectively, and receive a plurality of signals therefrom,respectively; and a diversity controller configured to selectivelyactivate and deactivate one or more receiver chains of the plurality ofreceiver chains in an idle mode to prevent unnecessary handovers from apresent network to another network.
 20. The receiver of claim 19,further comprising a quality estimation unit configured to determine areception quality of the receiver in the idle mode, wherein thediversity controller is configured to selectively activate anddeactivate one or more receiver chains in the idle mode based on thedetermined reception quality.